


Fellfucker

by AnonymouslyAfraid



Category: Undertale (Video Game)
Genre: Ectobits, Everyone is in heat because fukc, Idk just yell at me in the comments if i'm too vauge, Incest, Look this is rlly self indulgent okay, M/M, Monster Heat, Monsters in general have this ability tbh in this fic, Mpreg, Multi, Poly Relationship, Reader has the ability to have both parts, Sex, There is a continuation to this but only if anyone cares, Vauge magical stuff, reader is a monster
Language: English
Status: In-Progress
Published: 2017-02-09
Updated: 2017-02-24
Packaged: 2018-09-23 02:10:43
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 3,225
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/9636269
Author URL: https://archiveofourown.org/users/AnonymouslyAfraid/pseuds/AnonymouslyAfraid
Summary: (I'm sorry i'm shit at titles)You (the reader) are in a fucked up, but committed, poly relationship with the skeleton brothers in Underfell. How or why is left unstated, but at this point, both of them (and you,) are in heat.There may or may not be a preference to Papyrus, because apparently the author is fucking thirsty for him.Gonna fuckin get some Mpreg up in this shitUndyne is also appearing whenever i write the third chapeter. Boy i fuckin love Undyne





	1. Heat

You find them both in the kitchen, the rough sound of panting and the cabinets being banged against giving them both away- Papyrus is a sobbing mess, though quiet and scrabbling at the counter, tongue lolling out of his mouth as Sans dry humps him furiously against the counter. Sans is sweating and panting, hands curled around Papyrus' hips and a red glow coming from his shorts.  
You clear your throat, and he stops, quickly looking over. Papyrus drops his head down against the counter, his arms are trembling, as are his legs.  
"Yeah, doll?" He asks, rubbing along Papyrus' spine gently, earning a soft whine and a shiver.  
Your gaze lingers on the glow as you approach him from behind, wrapping your arms around his shoulders and pressing close. He chuckles, leaning back against you with a lazy grin.  
"Wanna help a guy out with his heat...?" He asks.  
"I n-need a break." Papyrus grumbles, slowly sinking to the floor.  
You hum, nodding and nuzzling the side of Sans' face, he hums in reply, returning the nuzzle. You give Papyrus a glance- he's got a faint glow in his armor, but he looks rather worn out, pale pink tears still running down his face. You'll come back to him later.  
"Alright, sweetheart. Let's take this upstairs..." He purrs.  
Papyrus shoots him a weak glare and flips him the bird. He returns the bird, snorting and pulling you out of the kitchen and to his room.  
You can feel you excitement growing, a bit of arousal growing in the pit of your stomach as Sans starts to strip. He hasn't even closed the door behind you two, there's no need for it right now.  
Sans tosses aside his jacket and shirt, teasingly sliding his shorts down slowly, the head of his glowing red cock peaking out over the waistband before slipping down his length. He becons you over, sitting on the edge of the bed. You pull off your own clothes, sitting down in his lap, forming a warm dripping vulva for him. He puts his hands over your hips, pulling you closer and running his hands down your thighs.  
"Mmm, fuckin gorgeous..." He mumbles, leaning forward to nuzzle against the crook of your neck. "Lucky to have a hottie like you, 'specially at a time like this..."  
You wrap your arms around his shoulders as he rocks up against you, rubbing his cock against your vag. He groans and shudders, and then shifts to start pressing into you slowly.  
"Fuck, babe, you're so goddamn delicious..." He mumbles, hands curling around your thighs.  
Before you can say anything, Sans is nibbling at your neck. His face is hot against you and his teeth don't quite puncture, lightly scraping and pressing, his warm breath coming in puffs as he starts rolling his hips.  
You start panting a bit, feeling each roll of his hips press the cock a little deeper into you, rubbing against your inner walls. Sans moves his hands back up to your hips, shoving the last bit of his length into you, causing you to gasp.  
"Hhnnn... Fuck, s'good..." He groans against your neck, having to pull back a bit before he bit too hard. "You good?"  
You nod, and Sans tightens his grip on your hips, lifting you up a bit- you help him, raising your hips up until he's only got the tip still inside. He pulls you back down against his dick, thrusting into you and causing you to moan suddenly. Sans chuckles, continuing to lift you up and drop you, thrusting hard each time.  
Soon, neither of you can stop making noise as Sans fucks you hard, the both of you holding eachother tight and trembling. Sans' breathing picks up, and so does the speed of his thrusts, his fingers curling into your hips.  
"Fuck- fuck, babe-!" He moans, "Oh god, oh god! I-i'm gonna, i'm c-com-!"  
Sans thrusts into you one final time, arching and shaking as his cum spurts into you, his hips twitching ever so slightly. You hit your peak on the third spurt, your mouth falling open with a silent cry of pleasure, and Sans rocks into you fast and shallow to help you through your orgasm.  
As you're both coming down, Sans lies back, pulling you down on top of him and kissing at your neck, wrapping his arms around you.  
You hear a small whine in the doorway, looking over your shoulder to see Papyrus there, face flushed and arousal dripping down his legbones.  
"Mmnah, m'beat." Sans mumbles, patting your back slightly. "He's all yours, doll."  
You pull yourself off of Sans' dick, pressing a small kiss to his cheek before getting up and heading over to Papyrus. Sans waves slightly and crawls into bed, asleep within moments.  
Papyrus perks up as you walk over to him, putting your hands on his shoulders. Only you and Sans get to see him so open and needy, allowing himself to be weak and soft.  
He pulls you in for a kiss, mouth open to invite you in- you accept, pressing your tongue into his mouth and tangling it around his. He shudders at the feeling, going along with it, and even pressing against you needily. You pull away from the kiss with a grin, savoring the desperate, lusty gaze Papyrus has focused on you. Before either of you go any further, you pull him towards his room.  
Papyrus wastes little time getting undressed- carefully setting aside his armor and boots, carefully folding up his cape. Even in heat and desperate to be fucked, he's still taking care to make sure everything's set aside neatly.  
"Could we..." Papyrus hesitates, and you follow him to the bed, "Could we... cuddle a bit?" He asks shyly, avoiding your gaze.  
You can't help but giggle a bit, nodding nonetheless. Papyrus smiles nervously, laying back on the bed and spreading himself out on display. You don't so much as summon your dick out as much as it summons itself, already at attention. He grins slyly, spreading his legs to expose the swollen lips of his pussy, glistening and slick. Your dick twitches at the sight, and you climb on top of him, struggling to keep yourself from simply fucking him senseless right then and there.  
"Gorgeous." He purrs, wrapping his arms around you and snuggling close. "You're so beautiful when you're turned on."  
You bite back a groan as he grinds up against you, pressing close and grinding your dick against his wetness. Papyrus gasps and make a soft noise, holding you tighter. You hug him, pressing small kisses against his collarbone and earning a strangled whine.  
"Aah, slower-" He pleads, and you slow your grinding, earning a pleased moan. "Ohhh, yes, like that~"  
Papyrus' eyes slide shut, and his mouth opens slightly to let out the small noises he keeps making, one of his legs wrapping around yours.  
You humm, drawing your tongue across his collar and up to his neck, sucking at the bone. Papyrus trembles, whining and pressing his hips up.  
"Hhhhnn, please..." He begs. "No more, i-i need you. Pl-please...!"  
You grin against his neck, stopping a moment and shifting a bit, your dick pressing against his entrance- his pussy welcomes you instantly, warm and easy to slide into. Papyrus moans loud, tilting his head back and spreading his legs a bit more.  
"Aahh! M-more, please, i-i can take it!" He says, tears already tricking down his cheekbones. "Pl-pleeeaase!"  
You press you dick into him a bit quicker, and his tongue lolls out of his mouth, panting and making those little noises louder. You kiss at his neck, and he trembles, holding you tighter. As you finally slide to the base, Papyrus lets loose a long groan, hips already rolling against yours a little.  
"Sl-slow, slowly-" He says quickly, voice strained with pleasure. "I st-still want to c-cuddle more..."  
You chuckle a bit at that, pulling back your hips slowly, enjoying the way Papyrus whimpers at the loss. You begin pushing back in slowly, peppering his face in little kisses.  
"Ahh- ah, nnnhh!" Papyrus moves one hand to cradle the back of your head, trembling beneath you. It's clear that the slow pace is killing him, but he doesn't tell you to go faster, only whines desperately.  
You decide to give him a little more relief, nuzzling him and beginning to thrust a bit quicker, earning a moan of delight. There's the sound of wet slapping as you pick up the pace, Papyrus wrapping his other leg around your waist.  
"Mmmhhoooh, god- god, god, please! Just a little- just a little-!" Papyrus shudders and yelps loud, hips stuttering up as you hit his sweet spot. "Th-there! There, pl-lease, m-more! There!"  
You gladly oblige, slamming into his sweet spot over and over, enjoying the way he writhes beneath you, unable to hold anything back, gasping out your name and bucking against you.  
"Pl-plea plea pl-plea-!" Papyrus gasps harshly and arches, mouth opening wide and legs trying to close up around you.  
His pussy clenches around your dick, walls pressing up against it, trying to milk you dry- with a cry you come, your thrusts becoming sloppy and slowing.  
"I love y-you, i love y-you-!" Papyrus sobs, shaking as tears pour down his face.  
Your thrusts come to a stop, and Papyrus is sobbing softly, nuzzling against your face. You sigh, kissing him softly and relaxing against him.  
"L-love you..." He mumbles, and you hum in agreement, wiping away his tears.  
The both of you fall asleep there, forgetting to pull apart.

**Notes for the Chapter:**

> ((As you can tell by this fic, i apparently really want to fuck Papyrus.))
> 
> If you really want this to be continued, please state in the comments! Though, be warned.  
>  The continuation definitely involves skeleton mpreg, so. If you're not into that just feel free to go 'ew gross fuck no' and bail.  
>  Also i'm rlly fuckin biased so if you have any ideas i might be open to those.


	2. New

**Summary for the Chapter:**

> Papyrus is pregnant, congrats. At least it wasn't you?
> 
> (( Warning: Mentions/depictions of vomiting. ))

You wake up early to the sound of vomiting, and Papyrus isn't laying with you in bed. You yawn and stretch, rubbing your eyes and sleepily heading to the bathroom, knocking on the door. You hear a cough, and a heave.  
"F-fuck off, i-i'm..." Papyrus coughs a bit more, vomiting again.  
You slowly open the door, spotting Papyrus by the toilet- he's shaking and vomiting up sickly red magic, hugging the toilet. He groans as he finishes, laying his head against the seat, tears pouring down his face. You coo softly, kneeling beside him and rubbing his back lightly. All he has on is a t-shirt and shorts, and he looks miserable.  
"Mmmuuhh... Get Sans..." He groans, holding his stomach. "L-lock the front d-door."  
You nod, getting up, leaning over to kiss his forehead briefly and flush the toilet for him.  
"Thanks..." He mumbles, relaxing against the toilet for a moment.  
You head downstairs first to lock the front door, grabbing one of Sans' discarded shirts from the couch and pulling it on, heading up to said skeleton's room. The door isn't closed, so you let yourself in and head over to Sans' bedside, where he's sleeping peacefully.  
"Sans." You mumble sleepily. "It's Papyrus, he's sick."  
Sans blinks awake, quickly sitting up and rubbing his eyes. You hand him a shirt to pull on, and retrieve your own pants from his floor to put on. Sans hurries to the bathroom, and you follow behind moments later.  
"Pap?" Sans calls, opening up the bathroom and heading over to his brother. "Hey, bro, you feeling okay?"  
Papyrus just groans, and Sans puts a hand to his forehead, frowning and shaking his head.  
"Didja eat somethin bad, or-"  
Before Sans can finish his sentence, Papyrus pulls up his shirt, revealing a thin pinkish ectostomach. There are small glimmers of magic flickering within. Magic trying to combine and form a SOUL.  
It's quiet for a few moments.  
"Uh." Sans says nervously, shakily reaching out to press his hand to the fragile tum, rubbing it slightly. "Whose is it, Pap? Do you, uh. Know?"  
Papyrus lightly slaps away Sans' hand, pulling his shirt back down and nodding, pointing... At you.  
Sans looks over his shoulder at you, mouth working for a moment, but no sound coming out.  
"... Congrats, you two. I guess." He mumbles. "D'you, uh. Do you want somethin? Like, water?"  
"W-water." Papyrus echoes, nodding slightly.  
"Alright, i'll getcha some water, gimme a minute." Sans mumbles, standing and patting your shoulder as he passes.  
"C'mere." Papyrus mumbles, opening up an arm in invitation. You nod, walking over to him and kneeling down.  
Papyrus pulls you into a weak one-armed hug, taking your other hand and resting it against his stomach. The light flutters of the working magic make your fingers tingle.  
"You did this to me..." He mutters, though he sounds more tired than angry or upset. "Fucker."  
You hug him, lightly rubbing circles into his stomach. He relaxes a bit more, resting his hand over yours and humming a bit. You can't help but think, even as tired and sick as he is- red shadows beneath his eyes and wearing the first thing he pulled on- he looks gorgeous. You kiss his cheek, and he smiles a little for a moment.  
"Do you want to keep it?" You ask softly, and he glares at you like the answer is obvious.  
"Mmmhm." He nods a little. "I hope... Hope it does something."  
You bite your tongue, but it doesn't help stop you from smiling, a wide grin splitting your face. Only mated monsters really pursued having children together... And that meant Papyrus had chosen you. That meant he loved and trusted you enough to keep the baby.  
You pepper his face and neck and kisses, and he laughs weakly, shoving at your face. Sans clears his throat, and you both look over.  
"... Am i interruptin somethin?" He asks, holding up a glass of water.  
Papyrus grunts, holding out an arm and making grabby hands at the water, Sans giving him the cup. Papyrus quickly drank half of the cup, spitting the water into the toilet before drinking the rest and setting the cup down.  
"Don't stop. It likes you better." Papyrus mumbles, leaning against you.  
Sans comes over and sits with you both, Papyrus offering a hand to hold and Sans accepting it. You hum curiously, continuing to gently massage Papyrus' stomach.  
"... Only calmed down when you did it." Papyrus grumbles, pulling Sans' hand close to kiss it before setting it down in his lap. "Don't w'nna have it get upset again."  
You nod, and Sans shoots you a curious look, glancing down at Papyrus' stomach briefly. You nod again.  
"What, don't they like uncle Sans?" Sans asks, snuggling up against Papyrus' side.  
"I don't even like uncle Sans, that much." He mutters, though he's clearly joking, a smile on his face.  
"Aww, bro, don't you love me though?" Sans replies, kissing Papyrus' knuckles.  
Papyrus snickers, shaking his head. "C'mere, jackass."  
The two of them kiss, resting their foreheads together. You watch, smiling a bit. The magic is starting to act up beneath your fingers.  
Papyrus stiffens a bit, batting away your hand and sitting up, pulling up his shirt. The light flickers are brighter, more frequent now.  
"It's happening-" He says softly, eyes wide.  
Both you and Sans lean over for a better look, all three of you watching with bated breath. For a few moments, the light flickers brightly in the center of Papyrus' stomach, getting ready. Papyrus tucks the shirt under his chin, grabbing and holding Sans' and your hands tightly, the both of you doing the same for eachother.  
The light flashes, and a tiny dark pouch begins to form, Papyrus' stomach darkening from a light pink to a bright red. A little pocket of maroon rests in his stomach, it looks like a tiny bean.  
"Oh my god-!" Papyrus sobs, tears running down his face.  
Sans laughs, grinning as he begins to cry as well.  
You laugh softly, leaning forward and kissing Papyrus' stomach as tears trickle down your cheeks.  
All three of you hug tightly, excited and happy to have witnessed the event of the baby finally forming fully.  
"It's so small-" Papyrus sobs, overwhelmed with emotion.  
"Shh, Pap. We know, s'gorgeous." Sans murmurs, rubbing his back.  
"So small," Papyrus repeats, sniffling. "Oh my god, my baby is so small- oh my god. They're so small."  
You kiss his cheek, and Papyrus laughs, choked with tears.  
"Our... Our baby is so tiny." Papyrus squeaks. "They're so small, they're so small..."  
Sans nods, humming. "We know, Pap. We saw."  
Papyrus' sobs harshen, and he leans against you and Sans more heavily, you both hold him tight as he's suddenly overwhelmed with greif.  
"Oh my god..." He croaks, shaking.  
"Shh, shh. We're right here, Pap. We gotcha. S'okay." Sans murmurs. "We gotcha."  
"God, what do we do about...?" Papyrus sobs again, curling up a bit. "H-how are w-we going to...?"  
"Hey, hey, shhh. S'okay, you're gonna be fine."  
Papyrus takes a shaky breath, exhaling in short bursts. He hugs you both a bit tighter, and then starts to calm down finally, sniffling again.  
"I'm okay." He mumbles. "I-i'm okay, it's passed."  
Sans rubs his back, patting it twice.  
"Pretty intense the first time, huh?" He asks, starting to pull away slightly.  
Papyrus sniffles, nodding and humming. Sans sits back, leaving you and Papyrus in the hug.  
"God... M'so tired." He says, leaning against you now that Sans has left the hug.  
"Yeah, takes a lotta magic. You okay?"  
Papyrus nods a little more, starting to go limp against you.  
"M'fine, jus... Tired. M'tired."  
"Get some rest, bro. Alright? I'll even bring you breakfast later." Sans says, smiling a little.  
"Mmmm." Papyrus shifts a bit to snuggle up against you, and you pull him into your lap, holding him. He falls asleep easily.  
Sans rubs his eyes, yawning a little.  
"Mhn, fuck. Now i gotta make breakfast." He grumbles. "... S'worth it though."  
He gently runs a hand across Papyrus' stomach, expression softening. You think you even see his left eye's magic relax a bit, fading a bit and contracting into an almost normal pupil.  
"Alright." He says softly, then looks up at you. "D'you want pancakes or eggs?"

You've carried Papyrus downstairs and laid down with him on the couch, holding him close as he rests. Sans follows behind you, but hooks a right into the kitchen to start cooking. You flick on the tv with a little magic construct- it never hurt to be a little bit lazy sometimes- and Papyrus stirs as Mettaton's show comes on. Though, he doesn't awaken, simply snuggling up to you a bit. You can hear Sans in the kitchen, the gentle clatter of things being clashed together and the stove being turned on. You take the time to examine Papyrus carefully in his sleep as Mettaton's chainsaw roars in the background.  
He looks a bit better than he did when he was clinging to the toilet, relaxed and peaceful. You give him a gentle kiss on the forehead and focus your attention on the TV again. It seems like Mettaton is tearing up human replicas, and a countdown in the corner of the screen flashes '00:25' and descending in red. As it reaches zero, he shuts off the chainsaw and smiles at the camera, tucking his hair behind his ear and leaning against the chainsaw itself.  
"Shit." Sans peaks out of the kitchen, "You uh, don't mind scrambled, do ya? Ah, what m'i sayin, of course you don't."  
He ducks back into the kitchen before you can give your input, and you shake your head with a soft sigh.

**Notes for the Chapter:**

> I think i owe an explanation, 'cuz i didn't wanna do an exposition dump in the middle of the chapter.
> 
> Monster babies, when their soul is first forming fully, take a lot of magic away from their 'mother' and cause some serious moodswings in the process.  
> It's kinda like getting punched in the stomach and experiencing 3 emotions in really quick succession. And then you're really tired.  
> Except Papyrus is probably used to being punched in the stomach, so.


End file.
